The invention relates to the field of multi-layer deposited then film structures.
The invention relates to a method of forming an assembly of stacked layers, in which method use is made of a recessed first layer on which a second layer filling up the recess is formed by depositing a material, and a polishing treatment is performed for forming a plane surface.
Such a method is known from EP-A 0 617 409 (PHN 14.428). In the known method, which is used in the manufacture of thin-film magnetic heads, a first layer is formed by depositing zirconium or quartz on a support, whereafter a recess is provided in this layer by removing material. Subsequently, a second layer filling up the recess is formed by depositing a soft-magnetic material. After the formation of the second layer, a mechanochemical polishing treatment is carried out until the first layer is reached, resulting in a plane surface formed by the first layer and the remaining part of the second layer present in the recess.
The above citation is hereby incorporated herein in whole by reference:
It has been found that in the known method, when the second layer is more wear-resistant than the first layer, it is difficult to control the polishing process in such a way that a smooth and plane surface is or has been obtained after reaching the first layer.
It is an object of the invention to improve the method described in the opening paragraph in such a way that a plane surface can be obtained in a simple manner during the polishing treatment.
According to the invention prior to forming the second layer, an intermediate layer restraining the polishing treatment is formed on the first layer by depositing a material which is more wear-resistant than the material of the second layer, and in that the polishing treatment is terminated after the intermediate layer has been reached.
When the polishing treatment, for example, a mechanochemical polishing treatment is being carried out, only the second layer, at least opposite and proximate to the recess, is polished initially. Since this layer has a homogeneous composition, the polishing treatment proceeds regularly in this phase and a smooth and plane polishing surface is obtained. The polishing rate changes at the instant when the plane in which the polishing treatment takes place reaches the intermediate layer. In fact, due to the larger wear resistance of the intermediate layer, the resistance against polishing increases. This means that a plane and smooth surface is ensured if the polishing treatment is terminated at that instant.
The method according to the invention is particularly important if the second layer has a larger wear resistance than the first layer. This is the case, for example, if the first layer is or has been formed from SiO2, Al2O3 or Si and the second layer is or has been formed from an FeNbSi, CoZrNb or FeSiAl alloy.
If the first and the second layer have the same wear resistance, it is favorable to use the intermediate layer as an indicator for terminating the polishing treatment. Also if the layers have mutually different wear resistances, it is favorable to use the intermediate layer as a visual indicator for terminating the polishing treatment. When using an indicator, the polishing treatment does not need to be temporarily interrupted for repeatedly measuring the quantity of material which is still to be polished off before a desired thickness of the second layer is reached and polishing should be terminated.
In an embodiment of the method according to the invention, at least substantially chromium and/or a chromium compound is used as a material of the intermediate layer. Although various materials may be used, it has been found that chromium and chromium compounds are particularly suitable as materials for forming the intermediate layer. Chromium and chromium compounds may be sputtered, which has the advantage that the composition and hence the wear resistance of the intermediate layer can be adjusted by adding nitrogen and/or oxygen during sputtering. If it is desirable to remove, prior to the formation of the second layer, parts of the intermediate layer in the recess or remainders of the intermediate layer outside the recess after polishing, this may be done by selectively non-chemical etching when chromium and chromium compounds are used. A further advantage of chromium and chromium compounds is that very thin layers, of the order of 20 to 50 nm, are sufficient to obtain a desired wear resistance.
The intermediate layer provided on the first layer may successfully serve as a protective layer during manufacture so as to prevent scratches which might be caused, for example, during polishing, and similar damages in the first layer. This is particularly important if the first layer has an insulating function such as, for example, in semiconductor structures. A damaged first layer may then easily give rise to short circuit in a conductor pattern provided on or in this layer.
In another embodiment of the method according to the invention, a chromium nitride and/or a chromium oxide and/or a chromium oxynitride is used as a chromium compound. A specific advantage of such compounds is that the quantity of nitride and/or oxide which is present determines the extent of wear resistance of the intermediate layer. In other words, the wear resistance is dependent on the quantity of oxide and/or nitride. By varying the quantity of oxide and/or nitride, a desired wear resistance, particularly determined by the material of the second layer, can thus easily be adjusted.
In another embodiment of the method according to the invention a non-magnetic, non-electrically conductive layer is used as the first layer. A further embodiment a magnetic and/or electrically conducting material is used as a material for the second layer. In another embodiment, a material corresponding to the material from which the first layer is formed is used as a material for the second layer. In all cases, the first layer may be or have been provided on a substrate or support. The first layer itself may also function as a support.
The invention also relates to an assembly manufactured by means of the method according to the invention.
The invention also relates to a magnetic head. Depending on the transducing element used, such a magnetic head may be an inductive or a magnetoresistive magnetic head and may be used in a device for magnetically writing and/or reading information. Such a device is, for example, a magnetic tape apparatus or a hard disk drive.
The invention also relates to a magnetic head unit in which a transducing element embedded in the second layer extends in the recess. Such a magnetic head unit may be used, for example, for writing information into and/or reading information from a magnetic optical storage medium.
It should be noted with respect to the claims that various combinations of characteristic features defined in the dependent claims are possible.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.